1. Field of the Invention
The present invention relates to a flexible printed circuit board (FPCB), and particularly to a FPCB for transmitting high speed signals.
2. Description of Related Art
FPCBs are light, soft, thin, small, ductile, flexible and support high wiring density. FPCBs can be three-dimensionally wired and shaped according to space limitations. Flexible circuits are typically useful for electronic packages where flexibility, weight control and the like are important.
Referring to FIG. 2, a conventional FPCB includes a signal layer and a ground layer 50, a differential pair 51 consisting of two transmission lines 52 and 54 is arranged in the signal layer, the ground layer is formed vertically beneath the signal layer and etched in a grid array. The layout in the ground layer 50 vertically beneath the transmission line 52 is different from that beneath the transmission line 54, noise is easily generated, which prevents the FPCB transmitting high speed signals.
What is needed, therefore, is a FPCB which can transmit high speed signals.